Cellular communications systems continue to grow in popularity and have become an integral part of both personal and business communications. Cellular telephones allow users to place and receive voice calls most anywhere they travel. Moreover, as cellular telephone technology has increased, so too has the functionality of cellular devices. For example, many cellular devices now incorporate personal digital assistant (PDA) features such as calendars, address books, task lists, etc. Moreover, such multi-function devices may also allow users to wirelessly send and receive electronic mail (email) messages and access the Internet via a cellular network.
Even so, as the functionality of cellular communications devices continues to increase, so too does the demand for smaller devices which are easier for users to carry. As a result, one style of cellular telephones which has gained wide popularity is the folding or “flip” phone. Flip phones typically have an upper housing with a display and speaker, and a lower housing or flap which carries the microphone. The keypad of such phones may be on either the upper housing or the lower housing, depending upon the particular model. The lower flap is connected to the upper housing by a hinge so that when not in use the upper and lower housings can be folded together to be more compact.
One example of a flip phone is disclosed in U.S. Pat. No. 5,337,061 to Pye et al. The phone has two antennas, a first one of which is mounted on the lower flap and includes a ground plane and an active monopole fed by a coaxial feed from electronic circuitry inside the phone. The flap is pivotally connected to the main or upper section of the housing, and is folded against the main section when not in use. Another similar antenna is fitted in the main section, and both antennas are connected to transceiver circuitry in the phone. The antennas are designed to introduce deliberate mismatch to provide an effective switching system between the antennas without the need for separate circuit elements. Other examples of flip phones are disclosed in U.S. Pat. Nos. 5,557,293 and 6,741,215.
Another compact style of cellular telephone is the so-called sliding phone. Sliding phones have upper and lower housings which are slidably connected to one another so that one housing slides over top of the other, and they slide relative to one another between a retracted position and an extended position. As such, these phones may also provide a relatively compact footprint when in the retracted position. Examples of sliding phones include the SL55 from Siemens Corporation, and the SCH-N330 from Samsung Electronics Co., Ltd.
One potential drawback of compact cellular telephone designs is that users with hearing aids may have difficulties using such phones. That is, the compact nature of such phones may place the user's hearing aid in close proximity to the phone's antenna. This, in turn, can cause undesired interference, which results in harmonics being introduced into the hearing aid. One approach for addressing this problem on a cellular telephone with an external antenna is disclosed in U.S. Pat. No. 5,819,162 to Spann et al., in which an electromagnetic interference (EMI) shield is mounted on a flap that extends away from the base of the phone during operation to form an enclosure about the user's ear for shielding the user's hearing aid from EMI. However, such a configuration may not be feasible on compact sliding phones which have internal, printed circuit board (PCB) style antennas.